Jest ava



Oct. 8, 1929. M. c. HOPKINS 1,730,507

LOUD S PEAKER il 0 1925 4 Sheets-Sheet l INVENTOR Nara/5 C Ha o/rm;

BY I W hm ATTORNEY 8, 1929- M. c. HOPKINS 3 LOUD SPEAKER Filed Dec. 22, 1925 4 Sheets-Sheet 2 I INVENTOR I Marry: /70 0k//7J BY h m a ATTORNEYS Oct. 8, 1929. M. c. HOPKINS 1,730,507

LOUD SPEAKER Filed Dec. 22 1925 4 Sheets-Sheet 5 INVENTOR I Marcus (THO/0470.5

' BY I fm-lg pm )fiwdu-.

ATTORNEYS Oct. 8, 1929. c, HOPKINS 1,730,507

LOUD S PEAKER Filed Dec- 22, 1925 4 Sheets-Sheet 4 BY fm' )g r [M ATTORNEY Patented Oct. 8, 1929 were s'mrss ATENT OFFECE WARE OF COLUMBIA, ASSIGNOR TO HOP NEW JERSEY, A CORPORATION OF DELA- LOUD-SPEAKER Application filed December 22, 1925. Serial No. 77,029.

The present invention embraces a loud speaker suitable for use on a radio receiving set, andalso suitable for use as an annunciator on wired radio systems, and in general, wherever speech current is to be translated into audible sound.

It is an object of'the present invention to provide a loud speaker of the cone type wherein the cone, which may be made of paper or like material, has its outer edge bent forward to form a brim or rim by which the cone is yieldingly attached to a wood frame capable of acting as a resonator to supplement the sound-producing action of the cone.

In the preferred form of the device the wood frame is of circular outline and has cut in one of its faces an annular groove bordered by a beveled edge to which the brim of the cone can be glued or otherwise secured. That portion of the disc outside of the cone acts as a sound producer or resonator, and that part of the disc within the periphery of the cone acts as a mechanical support for the electrical movement whereby the device is actuated.

Other objects and advantages will become clear from the following detailed description taken in conjunction with the accompanying drawings wherein Fig. 1 is a front elevation of the loud speaker;

Fig. 2 is a side elevation of the same;

Fig. 3 is a sectional elevation on the line 3-3 of Fig. 4;

Fig. 4 is a front elevation with the paper cone removed to disclose the electrical movement;

Fig. 5 shows the electrical movement in front elevation with certain parts in section;

Fig. (5 shows said element in side elevation;

F 7 is a transverse section on the line 7 of Fig. 5;

Fig. 8 is a plan view of the electrical movement;

Fig. 9 is a sectional detail of the laminated armature thereof;

Fig. 10 shows the slots in the adjustable pole shoe of the unit, and Fig. ll is a detail of one of the pole pieces.

The preferred embodiments disclosed in the drawings comprise a wood base 1 having a slot in which is glued the lower edge of a circular resonator 2. This resonator is preferably made of three ply wood. Three ply fir three-eighths of an inch thick is suitable, and there is advantage in having the grain of the inner ply 3 disposed at right angles to the grain of the two adjacent outer plies. An annular groove 4 is turned in this resonator, and at the outer edge of this groove the wood is beveled at 5 to form a seat to which may be glued the outwardly bent brim 6 of the sound producing cone 7. This cone may be made of paper. Paper of the quality known as cover paper is suitable. The cone can be cut from a flat sheet and then bent into shape and glued along a radial seam. The outer edge of the conical structure so formed is then bent at 8 to form an outwardly flaring brim. The brim will naturally take on a frustoconical form making an angle to the vertical plane substantially equal to the angle at which radial elements of the cone intersect the vertical plane. It is important that the outer part only of this brim 6 be fastened to the wood resonator at the beveled surface 5 for the inner portion of the brim is relied on to form a resilient support or hinge whereby the cone 7 may move bodily without substantial distortion. For a paper cone 12" in outside diameter the brim may be of an inch wide and the glued portion'may have a width of or thereabout.

The cone plays, not only on its front surface, but also on its back surface, and to prevent mufiling of its vibrations, there is advantage in cutting away a part of the wood disc 2 as by cutting three circular openings therein a, Z) and c as shown in F ig. 4. This leaves a spider of wood strong enough to support the electrical actuating movement but not obstructingtherearwardly projectedsound waves to such an extent as would cause troublesome muffling. That part of the disc which lies outside of the cone is the part mainly relied on to supplement the primary vibrations of the cone, and to act as a sounding board, particularly for tones in the lower range. though some of that part of the board within the periphery also acts to transmit vihrrnions to the air.

The electrical movement for actuating the cone comprises a permanent magnet 9 suit.- aoly clamped to the wooden disc 2 as by :1. cr bar 10 and machine screw 11. Secured to pole 1'2 of the magnet by a screw 13 (Fig. 5) is a pole piece 14 of irregular shape. This pole piece i i-is provided with an extension 15 which projects beyond the end of pole 12 and carries a pair of lugs 16 pressed out from the stock of the extension by a punching operation and serving to center the pole piece on the end of the pole when bolt 13 is tightened. The other magnet pole 17 is similarly provided with a pole piece 18 held in place by a screw 19 and carrying a transverse bolt 20 whereby the vibratory armature is supported.

The vibratory armature consists of a plurality of blued steel laminations 21, say four in number. spaced apart on bolt 20 by iron washers 22, with which the laminations make close magnetic contact. At their other ends the laminations are spaced apart by soft iron washers 2?), and are held in close contact therewith by a soft iron element 24, one end of which is riveted over to form an annular flange tightly holding the laminations and washers together. This element 24 is in part hollow to receive a transmission rod 26, preferably made of phosphor bronze and secured to element 24 by solder 27. The forward end of the transmission rod 26 passes through a hollow rivet 28 at the apex of the cone, and may there be rigidly attached by a soldered connection 29 (Fig. 3). Or, if desired, as shown'in Fig- 6. a set screw 30 may be used in place of or as supplemental to a soldered connection 31. Conical brass plates 32 and 33 serve to strengthen the apex of the cone and are held in tight. engagement with the paper at. the apex of the cone by the hollow rivet 28.

The electron'iagnet to which speech current is delivered for actuating the armature comprises a simple solenoid 34. About (3000 turns of No. 40 enameled wire mounted on a balzclite or composition spool 35 is suitable "for this purpose. An insulating face plate 3-36 may be used as a guide and anchor for the leading in wires 37 and 2-38. Mounted to move within this coil is a soft iron poie shoe 39, a portion of which is threaded at 40 for engagement with threads cut in the pole piece 14. There is. also provided a knob 41 positioned at the back of the wood resonator and by which pole shoe 39 may be advanced or retracted to increase or decrease the air gap be tween it and the opposing element 24. The pole shoe is preferably provided with intersecting slots 42 and 43 10) to reduce eddy currents.

Fig. 11 shows pole piece 14 in rear elevation. I find that it is advantageous to first driil this pole piece to receive the threaded pole shoe 39 and then to shit it at -24 through the tapped hole. The two lingers thus pro duced are then squeezed inward toward one another by such an extent as may be needed to give a frictional grip on the t-hreadec portion 40 of the pole shoe 3!). This prevents that pole shoe from working loose during shipment and also holds the pole shoe in rigid position irrespective of the vibration to which the pole shoe subjected when in actual use. This slot it has the further function of reducing eddy current losses in that part of the pole piece lying nearest to coil 34. This one expedient increases the effectiveness of the device to a very noticeable extent.

\Vith the elements constructed and arranged as above described a speech current passed through winding 3*. as from a radio receiving set or a wire annunciator system or circuit, will produce a correspmiding vibration of the laminated armature and such movement of the transmission rod 26 as to translate the electrical impulses into-aauliblc sound thereby in effect reproducing the speech or other signal represented by the speech current.

The conical diaphragm 7 can move bodily because of its yielding or hinged connection with the wood resonator. and I have found is capable of transmitting its vibrations through the hinge to the wood. This is particularly true with respect to tones low in the musical scale. The wood takes up the vibrations and together with the cone transmits the vibrations to the surrounding air with results that are highly satisfactory. The pole shoe can be advanced or retracted through coil 34 by suitably manipulating the knob 41, and in this manner the width of the air gap can he coo1 lina.ted lo the. strength of the. signals being received. Any expansion or contraction of the diaphragm due. to atmospheric conditions is not of serious consequence because the free end of the armature can move with the cone and rezuljustment of the air gap to compensate for such changes requires nothing more than manipulation of knob 41.

The loud speaker or annunciator above described may be made in various sizes. and compact. rugged, and inexpensive to build. \Vhen built into a radio receiving set or cabinet, or when used as an accessory in other articles of merchandise. such as reading lamps. the base. 1 may be omitted.

Various changes in details of parts. and in their grouping may be n'iade without departing from the spirit of the invention as defined by the appended claims. In my copending application. Serial No. 77.033. tiled December 22, 1925 I have broadly claimed a diaphragm having a forwardly flaring brim portion. and a wooden sound board to which said brim portion is attached. The said application also contains claims directed broadly to the combination of a wooden sound board, a conical diaphragm mounted on said board, and actuating means connected to the diaphragm.

I claim:

1. In a cone type loud speaker the combination of a sound board, an actuating movement carried thereby, and a cone positioned at one side of the sound-board and covering the central portion thereof and operatively connected to said movement, at least a portion of said sound board extending across the base of said cone.

2. In a cone type loud speaker, the combination of a wooden sounding board, a conical diaphragm mounted thereon and actuating means connected to the diaphragm, at least a portion of the sounding board extending across the base of the cone, said actuating means being supported on said sounding board.

3. In a cone type loud speaker, the combination of a fiat sounding board having an annular groove and a vibratory cone mounted on the front face of said board with its edge in said groove.

4. In a cone type loud speaker, the combination of a wood sounding board having an annular groove, and a vibratory cone having its periphery positioned in said groove.

5. In a cone type speaker, the combination of a flat sounding board having an annular groove with a beveled edge, and a vibratory cone having a forwardly bent brim glued to the beveled edge of said groove.

6. In a cone type speaker, the combination of a wood sounding board having an annular groove, and a vibratory cone flexibly secured to the front face of said board with its periphery positioned in said groove.

7. In'a cone type loud speaker, a sounding board having openings therethrough to form a spider, a cone secured to the face of said board outside of said spider, and an actuating movement housed within said cone and supported by said sounding board near the center of said spider.

8. In a cone type loud speaker, the combination of a sounding board having an ann ula r groove with a beveled edge, a vibratory cone flexibly secured to said beveled edge, and an actuating movement supported by said sounding board and operatively connected with the apex of said cone.

9. In a cone type loud speaker, a sounding board cut away near its center to form a spider, a paper cone of less diameter than said sounding board and having a forward- 1y bent brim secured to said sounding board outside of said spider, and an actuating movement supported by said spider and operatively connected to vibrate said cone.

10. In a cone type loud speaker, the combination of a wood back, an actuating movement carried thereby, and a cone supported at the front of said wood back and covering the central portion thereof and operatively connected to said movement at least a portion of said wood back extending across the base of said cone. i

11. In a cone type loud speaker, the combination of a plane wood back, a cone of lessor periphery yieldingly engaging the front face thereof. andan actuating movement connected with said cone and housed between said cone and said back, said back being cut away in part to facilitate the propagation of sound from the rear of said cone.

12. In a cone type loud speaker, the combination of a wood base, a vertical wood back carried thereby and having holes therethrough for the transmission of sound, an actuating movement supported on the front face of said back near its center, and a vibratory cone of lesser diameter than said back and covering the holes therein, and also covering said actuating movement, the apex of said cone being operativelyconnected with said actuating movement.

13. In a cone type loud speaker, the combination of a vertical wood back having sound transmitting openings therethrough, said back having an annular groove in the front face thereof outside of said openings, and a vibratory cone mounted for free bodily movement and having its periphery in said groove.

14. In a cone type loud speaker, the combination of a wood back having openings therethrough, an annular groove in the front face of said back outside of said openin s, an actuating movement mounted on t 1e front face of said board near its center, and a vibratory cone housing said movement and having its edge yieldingly connected with said wood back at said groove.

15. In a cone type loud speaker, the combination of a wood back having an annuluar groove in the front face thereof, a vibratory cone having its edge in said groove, and a yielding element between said edge and the wood of said groove.

16. In a cone type loud speaker, the combination of a wood back with sound transmit-- ting openings therethrough an actuating movement supported on the front face of said wood back near its center, a paper cone of less diameter than said wood back and housing said actuating movement, and a yield ing element between the edge of said cone and said back adapted to give physical support to the cone while permitting bodily movement thereof when acted on by said movement.

17. In a cone type loud speaker, the combination of a flat wood back, an actuating movement carried thereby, a cone supported at the front of said wood back with its concave side toward said back, said back extending beyond the periphery of the cone and having portions extending across the base of the cone.

18. In a cune type loud speaker the combination of a plane back of wood veneer, a cone of lesser periphery with its edge spaced from said back by an annular yielding element and an actuating movement operatively connected with said cone and housed between said cone and said back, said back being cut away in part within the periphery 0f the cone.

In testimony whereof I aifix my signature.

MARCUS C. HOPKINS. 

